Pins are commonly used to join components that rotate in relation to each other. A pin passes through openings in each of the components and is retained by mechanical means such as friction or by use of a retainer(s) on the pin or component. The openings and the pin surface form bearing surfaces as the component pivots.
Mining equipment uses pins extensively to join very large components used in highly abrasive environments. FIG. 1 shows a dragline bucket system 10 used in open pit mining operations with rigging for moving the bucket. The rigging handles extreme loads in pulling the bucket to collect earthen material and lifting the filled bucket. The bucket 12 is pulled forward by drag chain 16 attached to hitch 18 on the front of the bucket by drag links 14. Teeth on the lower lip engage and initially gather the earthen materials into the bucket.
Once filled, the bucket is lifted by cables connected to an upper hoist rigging assembly 20 connected to the bucket by upper hoist chains 22 and lower hoist chains 24 to trunnions 26 of the bucket. Once lifted off the ground the bucket can be repositioned to a dump site for spoiling material. When tension is released on the drag link, the dump cable 28 passing through the dump block 30 releases allowing the bucket to rotate about the trunnion point well back of the center of gravity and tip forward so that the earthen materials are dumped from the bucket. The connections between the cables, chains and the bucket include one or several pins to secure the components to adjacent components.
In aggressive environments, the pins and the components wear quickly and require frequent replacement. Dirt, rocks, and other debris abrade the dragline bucket and the rigging as they contact or slide against the ground. Connections between the various elements also experience wear in areas where surfaces of the elements bear against each other and are subjected to tensile, compressive, or various other forces. Following a period of use, therefore, portions of the dragline excavating system are subjected to maintenance to permit worn or otherwise damaged elements to be inspected, repaired, or replaced.
Rigging components for dragline mining vary in size and weight. The dump block can weigh several thousand pounds, and the pins and links of the chain can each weigh several hundred pounds. Replacing the pins can require heavy lifting equipment for each component and each component has to be aligned for the pin to be removed or installed. The installation operation can be hazardous for the installers. Cutting away and reattaching retention plates that often retain the pins can be time consuming and expensive.
A pin assembly that can be installed with less handling and processing while incurring fewer hazards to the operators would be advantageous.